The When and Why of Static Stretching

In this article, we will be examining the rules for static and dynamic stretching. Physiologically of course.

First, we need establish what the common rules are:

1. Save static stretching until the end of a workout.
2. If there are athletic movements, then it is a good idea to stretch the opposite of the movement that may slow down said movement. For example, hip dominant movements may benefit from stretching the hip flexors. If you need mobility to do the full range of motion of a movement, then static stretching is fine.

The quick physiology…

Static stretching basically forcibly lengthens your muscles (via sacromere stretching) and inhibits the muscle spindles which are located in the belly of the muscle. These muscle spindles are sensory receptors that send feedback to the central nervous system. If the muscle is lengthening too rapidly, the CNS will send motor feedback (reflex) to the muscles telling them to contract. This is the body’s protective mechanism often called the “stretch-shorten cycle” which is there to prevent the muscle from straining or tearing. Most of the studies show that stretching upwards of 60-90 forcible inhibits this stretch-shorten cycle respond which may decrease power output.

The etiology of strained/pulled muscles

All strains/pulls are pretty much the same so let’s take a look at one of the more common ones — the hamstring strain.

Now what happens often in kicking sports and sprinting is that the hamstrings get fatigued very quickly. This is because the hamstrings do double duty as primary movers with the glutes in hip extension, and also act as an eccentric control for the the lower leg in the knee drive forward (image 1-6 for the left hamstring).

This physiological data has a two implications:

1. Without stretching, as the muscles fatigue, if they do not have enough strength-endurance to contract to prevent lengthening you get a strain. This is what happens with kicking sports and sprinters if their hamstring strength-endurance is not well developed regardless of static stretching or not.
2. With stretching, the muscle spindles act to reflexively activate the muscle to keep it from elongating too quickly too far in the ECCENTRIC phase. If the strength-endurance of the person is too low (novice runners) or the person is extremely powerful (extremely fast runners) or somewhere in between the addition of static stretching may increase the chance of a hamstring strain.

As we can see the potential for injury may increase especially in sports or exercises with a large eccentric component if we static stretch the muscle before exercise.

Note: Groin strains are similar to hamstring strains because of their dual nature in kicking and sprinting sports as well.

Energy conservation

This manifests itself in 2 ways.

1. Static stretching before a workout decreases the ability to exhibit maximum power or strength up to approximately 25-30 minutes after stretching. So it is not a good to static stretch before workouts.
2. If the resting muscle length is too long (too much static stretching overall), then one of the problems you encounter is that the stretch-shorten reflex does not work as well. Excessive flexibility such as the splits may be counterproductive for sports that do not require it because it will decrease your ability in power or strength movements.

For example, the stretch-shorten cycle is also used for energy conservation such as “bouncing” out of the bottom of the squat with the hammies (Oly lifting, weightlifting, etc.) as they lengthen under tension, or in the plyometric moment on the calves/hamstrings during sprinting.

Examining the hip flexors exception

The one exception is stretching the hip flexors before any explosive hip extension movement. We know that as a muscle lengthens rapidly the stretch-shorten cycle sends feedback to the CNS which relays the message to tell it to contract. In hip extension, the hip flexors are performing the eccentric component (as well as the rectus femoris) resisting against the extension and hyperextension of the hip.

We want to static stretch them to inhibit the stretch-shorten cycle so that we can increase the power of our hip extension/hyperextension allowing us to sprint faster, squat more powerfully, or anything that requires power or strength in a hip extension movement (which is almost every lower body exercise).

Examining the mobility exception

If you cannot move full range of motion into movement such as the squat, it may be beneficial to stretch your hamstrings or calves or quads before performing squats. The reason for this is that performing the full range of motion of the movement is of higher importance than the application of increased force output during the exercise. Full range of motion movements tend to have more beneficial carryover in terms of both strength, hypertrophy, and injury prevention into athletic movements in the long run. There are a few exceptions, but for most people reading this article who aren’t elite athletes they won’t apply.

In conclusion

Thus, we come to the few conclusions we arrived in the introduction (underlined) with a little bit added on as clarification, plus an additional rule.

1. Save static stretching until the end of a workout. BUT only static stretch if you need the flexibility for your sport. Flexiblity that is sufficently developed for sport is fine where it is, and OVERdeveloped flexibility may have to be remedied with strength/power training without any static stretching.
2. IF there are athletic movements, then it is a good idea to stretch the antagonist muscles to them. For example, the hip movement and hip flexors. Most athletes’ hip flexors are too strong and short because we sit a lot. But if you’re a lucky person where yours are underdeveloped and weak then be wary of static stretching them until they are sufficiently strong because of the potential for groin strains.
3. Static stretching may be useful before if you need range of motion increases to properly perform full range of motion of a movement. If our sport requires flexibility in it (such as gymnastics and the splits), then clearly static stretching before it may be beneficial to hit the positions.

Similarly, with novice lifters if flexibility is limiting their ability to hit technically correct positions (aka bottom of the squat has butt winking with tight hamstrings), then use static stretching so they can improve their form for their lifts. This is something that must be addressed both before and after lifting to improve their ability to do the lifts technically correct.

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This article was originally published August 19, 2009 on Eat Move Improve. Updated Dec 2016. 

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